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Category:   Application (Generic)  >   GNU GRUB Vendors:   GNU [multiple authors]
(Red Hat Issues Fix) GNU GRUB Authentication Bug Lets Local Users Bypass Authentication and Gain Elevated Privileges
SecurityTracker Alert ID:  1034423
SecurityTracker URL:  http://securitytracker.com/id/1034423
CVE Reference:   CVE-2015-8370   (Links to External Site)
Date:  Dec 15 2015
Impact:   Root access via local system
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): 1.98 - 2.02
Description:   A vulnerability was reported in GNU GRUB. A local user can obtain elevated privileges on the target system.

A local user can bypass authentication and gain full control of the target system.

The vulnerability resides in 'grub-core/lib/crypto.c' and 'grub-core/normal/auth.c'.

The original advisory is available at:

http://hmarco.org/bugs/CVE-2015-8370-Grub2-authentication-bypass.html

Hector Marco and Ismael Ripoll reported this vulnerability.

Impact:   A local user can obtain full control of the target system.
Solution:   Red Hat has issued a fix.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2015-2623.html

Vendor URL:  rhn.redhat.com/errata/RHSA-2015-2623.html (Links to External Site)
Cause:   Boundary error
Underlying OS:  Linux (Red Hat Enterprise)
Underlying OS Comments:  7

Message History:   This archive entry is a follow-up to the message listed below.
Dec 15 2015 GNU GRUB Authentication Bug Lets Local Users Bypass Authentication and Gain Elevated Privileges



 Source Message Contents

Subject:  [RHSA-2015:2623-01] Moderate: grub2 security and bug fix update

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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Moderate: grub2 security and bug fix update
Advisory ID:       RHSA-2015:2623-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2015-2623.html
Issue date:        2015-12-15
CVE Names:         CVE-2015-8370 
=====================================================================

1. Summary:

Updated grub2 packages that fix one security issue and one bug are now
available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having Moderate security
impact. A Common Vulnerability Scoring System (CVSS) base score, which
gives a detailed severity rating, is available from the CVE link in the
References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Client (v. 7) - x86_64
Red Hat Enterprise Linux Client Optional (v. 7) - x86_64
Red Hat Enterprise Linux ComputeNode (v. 7) - x86_64
Red Hat Enterprise Linux ComputeNode Optional (v. 7) - x86_64
Red Hat Enterprise Linux Server (v. 7) - aarch64, ppc64, ppc64le, x86_64
Red Hat Enterprise Linux Server Optional (v. 7) - aarch64, x86_64
Red Hat Enterprise Linux Workstation (v. 7) - x86_64
Red Hat Enterprise Linux Workstation Optional (v. 7) - x86_64

3. Description:

The grub2 packages provide version 2 of the Grand Unified Bootloader
(GRUB), a highly configurable and customizable bootloader with modular
architecture. The packages support a variety of kernel formats, file
systems, computer architectures, and hardware devices.

A flaw was found in the way the grub2 handled backspace characters entered
in username and password prompts. An attacker with access to the system
console could use this flaw to bypass grub2 password protection and gain
administrative access to the system. (CVE-2015-8370)

This update also fixes the following bug:

* When upgrading from Red Hat Enterprise Linux 7.1 and earlier, a
configured boot password was not correctly migrated to the newly introduced
user.cfg configuration files. This could possibly prevent system
administrators from changing grub2 configuration during system boot even if
they provided the correct password. This update corrects the password
migration script and the incorrectly generated user.cfg file. (BZ#1290089)

All grub2 users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues.

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

5. Bugs fixed (https://bugzilla.redhat.com/):

1286966 - CVE-2015-8370 grub2: buffer overflow when checking password entered during bootup
1290089 - Grub password broken by update from RHEL7.1 to RHEL7.2

6. Package List:

Red Hat Enterprise Linux Client (v. 7):

Source:
grub2-2.02-0.33.el7_2.src.rpm

x86_64:
grub2-2.02-0.33.el7_2.x86_64.rpm
grub2-debuginfo-2.02-0.33.el7_2.x86_64.rpm
grub2-efi-2.02-0.33.el7_2.x86_64.rpm
grub2-tools-2.02-0.33.el7_2.x86_64.rpm

Red Hat Enterprise Linux Client Optional (v. 7):

x86_64:
grub2-debuginfo-2.02-0.33.el7_2.x86_64.rpm
grub2-efi-modules-2.02-0.33.el7_2.x86_64.rpm

Red Hat Enterprise Linux ComputeNode (v. 7):

Source:
grub2-2.02-0.33.el7_2.src.rpm

x86_64:
grub2-2.02-0.33.el7_2.x86_64.rpm
grub2-debuginfo-2.02-0.33.el7_2.x86_64.rpm
grub2-efi-2.02-0.33.el7_2.x86_64.rpm
grub2-tools-2.02-0.33.el7_2.x86_64.rpm

Red Hat Enterprise Linux ComputeNode Optional (v. 7):

x86_64:
grub2-debuginfo-2.02-0.33.el7_2.x86_64.rpm
grub2-efi-modules-2.02-0.33.el7_2.x86_64.rpm

Red Hat Enterprise Linux Server (v. 7):

Source:
grub2-2.02-0.33.el7_2.src.rpm

aarch64:
grub2-debuginfo-2.02-0.33.el7_2.aarch64.rpm
grub2-efi-2.02-0.33.el7_2.aarch64.rpm
grub2-tools-2.02-0.33.el7_2.aarch64.rpm

ppc64:
grub2-2.02-0.33.el7_2.ppc64.rpm
grub2-debuginfo-2.02-0.33.el7_2.ppc64.rpm
grub2-tools-2.02-0.33.el7_2.ppc64.rpm

ppc64le:
grub2-2.02-0.33.el7_2.ppc64le.rpm
grub2-debuginfo-2.02-0.33.el7_2.ppc64le.rpm
grub2-tools-2.02-0.33.el7_2.ppc64le.rpm

x86_64:
grub2-2.02-0.33.el7_2.x86_64.rpm
grub2-debuginfo-2.02-0.33.el7_2.x86_64.rpm
grub2-efi-2.02-0.33.el7_2.x86_64.rpm
grub2-tools-2.02-0.33.el7_2.x86_64.rpm

Red Hat Enterprise Linux Server Optional (v. 7):

aarch64:
grub2-debuginfo-2.02-0.33.el7_2.aarch64.rpm
grub2-efi-modules-2.02-0.33.el7_2.aarch64.rpm

x86_64:
grub2-debuginfo-2.02-0.33.el7_2.x86_64.rpm
grub2-efi-modules-2.02-0.33.el7_2.x86_64.rpm

Red Hat Enterprise Linux Workstation (v. 7):

Source:
grub2-2.02-0.33.el7_2.src.rpm

x86_64:
grub2-2.02-0.33.el7_2.x86_64.rpm
grub2-debuginfo-2.02-0.33.el7_2.x86_64.rpm
grub2-efi-2.02-0.33.el7_2.x86_64.rpm
grub2-tools-2.02-0.33.el7_2.x86_64.rpm

Red Hat Enterprise Linux Workstation Optional (v. 7):

x86_64:
grub2-debuginfo-2.02-0.33.el7_2.x86_64.rpm
grub2-efi-modules-2.02-0.33.el7_2.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from
https://access.redhat.com/security/team/key/

7. References:

https://access.redhat.com/security/cve/CVE-2015-8370
https://access.redhat.com/security/updates/classification/#moderate

8. Contact:

The Red Hat security contact is <secalert@redhat.com>. More contact
details at https://access.redhat.com/security/team/contact/

Copyright 2015 Red Hat, Inc.
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